Our long-term objective is to understand how growth and differentiation are regulated in epithelia and to identify the mechanisms by which cells escape normal controls and behave malignantly. We are studying human mesothelial cells (HM) - the simple squamous epithelial cell type that lines the inner body cavities - and human keratinocytes (HK) - the cell type that forms stratified squamous epithelia such as that of the epidermis, oral cavity, esophagus, and exocervix. The mechanisms responsible for the maintenance of normal tissue homeostasis, the rapid but transient division and migration during wound repair, and the dysplasia and invasiveness of malignant cells are yet unknown for mesothelial cells and keratinocytes, which are among the most abundant cells in the body. Mesothelioma and oral and esophageal squamous cell carcinoma are important clinically because they are usually diagnosed at a stage too far advanced to permit complete surgical resection and radiation/chemotherapy are almost never curative. Recently, we and others have recognized that FGF, a polypeptide mitogen which has long been studied for its role in angiogenesis, may be the central character in normal HM and HK regulation and may also be involved in the uncontrolled growth exhibited by their malignant forms. We propose to characterize an FGF-like factor which we have found to be secreted by many naturally and experimentally transformed HM and HK cell lines. We will determine whether its expression and autocrine action is essential for mitogenic stimulation of normal cells by interfering with its expression with antisense oligo- nucleotides. We will introduce a constitutively expressed FGF gene into normal HK, graft the cells to the dermis of athymic mice, and assess the consequences of autocrine FGF in vivo on commitment to and expression of terminal differentiation by immunohistological evaluation of the tissue formed. Lastly, we will seek to identify genes that trans-activate FGF gene expression as a step in the process of malignant transformation in HM and HK cells by retroviral insertional mutagenesis of normal HM cells and by isolating tumor-derived genes that confer FGF-independence upon NIH3T3 cells.